Removing External Users from SharePoint Online

SharePoint Online makes it extremely easy to share sites, lists, libraries or documents with external parties. When you want to share something you can use the sharing feature on SharePoint, enter an email address and a custom message and click send.

When it comes to removing the external user from the site collection, and not just their access but all reference to that user so that they don't appear in the suggested contacts, this requires a few steps.

Pre-requisites

First you will need to download the SharePoint Online Management Shell.